GNSS Flight Recorders

With the advent of satellite navigation equipment at an affordable price, glider pilots can provide precise evidence of position without using either ground-based observers or photography. There is a Technical Specification for IGC-approved Flight Recorders, which includes the provision of a pressure altitude sensor in addition to a GNSS (Global Navigation Satellite System) receiver. Functions such as Pilot Event (PEV), task declaration and navigation to turn points, may also be incorporated. The pressure altitude system in an IGC-approved FR is a barograph in its own right, and is subject to normal barograph rules (such as on accuracy and calibration). Most IGC-approved GNSS FRs are units which integrate the GPS and other functions all in one sealed case, although for badge flights up to and including diamonds, FRs have been approved which connect by cable to a separate proprietary GPS unit such as named Garmin models.

GNSS and pressure altitude data is recorded in the form of regular fixes, the fix interval being governed by pilot's setup of the Flight Recorder. The maximum fix interval set on the FR and allowed for a flight to be validated to IGC rules is one minute, and pilots approaching the Observation Zones for Turn Points often set short fix intervals as low as 1 second (if the FR allows such a fix interval), in order to spend the minimum possible time in the Observation Zone.

OBSERVATION ZONE VALIDATION At least one valid fix must be in the Observation Zone (OZ), or a straight line joining two consecutive valid fixes must pass through the OZ.

Flight data is stored in the FR memory, and after flight is downloaded from the FR either to a PC, memory card or USB memory stick (depending on the characteristics of the Recorder).

For download to a PC and validation of the electronic flight data, free files are available through this web site. The MS Windows-based IGC Shell Program works with each manufacturer's DLL file. For older recorders there are short program files for transfer of the flight data (DATA.EXE), conversion to the IGC data file format (CONV.EXE), and for validation of electronic security (VALI-EXE) using standard electronic security systems such as RSA. For current recorders these functions are part of the IGC Shell program and the manufacturers' DLL files.

Where downloading of the IGC file is direct to a memory card or USB memory stick, the Validation function of the IGC Shell program must be used to check the integrity of the data in the IGC file.

There are also programs for analysis of the IGC data file format. Some analysis programs are incorporated in the FR manufacturer's full software programs, and some are independent of FR manufacturers' programs. There is no obligation for a FR manufacturer to have a proprietary program for data transfer and analysis, as the short program files and independent analysis programs, provide these functions.

For all FAI/IGC badge flights, and record flights to IGC criteria, rules for GNSS Flight Recorders may be found in the following documents. Rules for competitions are decided by the competition organisers, who may choose to use IGC rules, variants of them, or local rules of their own.

• FAI Sporting Code Section 3 and Annexes
• Technical Specification for IGC-approved GNSS Flight Recorders

The IGC set up a "GNSS FR Approval Committee" (GFAC) whose task it is to test FRs for their suitability for documenting badge and record flights according to the IGC rules. The Terms of Reference of GFAC are in Annex B to the Code. The following documents and software are made available on the IGC web site by GFAC on behalf of IGC:

• List of IGC-approved FRs, with links to complete IGC-approval documents.
  Note for Microsoft Internet Explorer users: For some reason the links in the above PDF document to the approval documents do not work in Internet Explorer. Links have therefore been added to the bottom of this page.
• List of programs for the analysis of IGC files, with links to their web sites.
• Freeware that is available on this web site includes programs for data transfer from a recorder to a PC, conversion to the IGC format (where an intermediate format is used by the recorder manufacturer) and validation of the flight data file for correct origin and that it is in the same state as when initially downloaded. Such programs are available for the MS Windows operating system and also, for older types of recorder, in DOS format. The MS Windows version works through the free IGC Shell program which is used with a free Data Link Library (DLL) file that is produced by the recorder manufacturer and should be placed on the PC in the same directory as the IGC Shell program. DLL files for different manufacturers can be placed in this directory and a list of manufacturers for which the DLL files are in the directory appears in the IGC Shell menu when IGC-SHELL.EXE is executed.

Each manufacturer is allocated a three-letter code by IGC that is included in the title of the DLL and DOS files, so that these files can be specific to the protocols used by that manufacturer. The three-letter code is normally the first three letters of the name of the organisation, or in some cases its initials. Codes are allocated by the GFA Committee and are given in the IGC Specification document, Appendix 1, para 2.5.6. Allocations are made when necessary between publication of amendments.

The DLL file names have the form IGC-XXX.DLL where XXX is the manufacturer=s IGC three-letter code and fulfil transfer, conversion and validation functions. The DOS short program files are DATA-XXX.EXE for data transfer, CONV-XXX.exe for conversion to IGC format, and VALI-XXX.EXE validation of electronic security.

Gliding organisations are encouraged to take copies of the freeware files so that pilots needing an Official Observer to take and store the flight data, can do so as soon as possible after the flight as required by IGC rules and procedures.

Are you thinking of developing a flight recorder? If so, please read this important notice.